Method of manufacturing a composite disc structure and apparatus for performing the method

ABSTRACT

A method of making composite discs continuously, including forming for each disc a first, a second layer, and a third support layer, each support layer being disc shaped and having a first surface with information indicia. An information layer is added to each support layers respectively. The said first and third support layers are positioned in a facing relationship, with the first and third information layers being adjacent. The third support layer is then separated from the third information layer, which thus remains attached to the first support layer. The first and second support layers are then joined. These steps are performed on a manufacturing line with conveyor belts transferring the support layers from station to station.

BACKGROUND OF THE INVENTION

[0001] A. Field of Invention

[0002] This invention pertains to a method of manufacturing multilayerdiscs, such as DVD/CD discs and the like, and more particularly, to amethod and apparatus in which the various subassemblies or components ofmultilayer discs are made and assembled in a continuous manner.

[0003] B. Description of the Prior Art

[0004] Early optical discs, such as CD discs, were made with only asingle information layer which was readable by a laser beam directedthrough one surface of the disc. Novel techniques were used to extendthe capacity of discs. High capacity discs are now available, which mayhave several information layers, each layer being readable by a laserfrom one surface of the disc. These high capacity discs are known asDVDs and are available in several flavors, such as DVD-5, DVD-9 and soforth, indicating a nominal capacity of 5 Gb, 9 Gb, etc.

[0005] Several types of DVDs are also made that are laser readable onboth sides including dual layer DVD/single layer DVD (DVD-4); dual layerDVD/dual layer DVD (DVD-8); Single layer/CD (DVD +); and dual layerDVD/CD. These discs are constructed by making two separate substrates,each substrate having at least one information layer (using either a CDor a DVD format) and then bonding the two substrates together, back toback. However, until now all these types of DVDs couls only be made in abatch mode. This operation is slow, labor intensive and thereforeexpensive.

OBJECTIVES AND SUMMARY OF THE INVENTION

[0006] It is an objective of this invention to provide a method ofmaking multilayered discs of the kind having information layer on twosides, wherein said discs are made in a continuous fashion.

[0007] A further objective is to provide a method and apparatus in whichmulitlayered discs are made on a continuously moving assembly line.

[0008] Yet another objective is to provide a method for continuouslymaking discs which can be performed without making major and extensivechanges in existing equipment.

[0009] Yet a further objective is to provide a method and apparatus thatcan be used to make different kinds of discs, including DVD/CD discs.DVD/DVD discs, etc.

[0010] Other objectives and advantages of the invention shall becomeapparent from the following description.

[0011] Briefly, the discs are manufactured using in a continuous manneron a manufacturing line, with each disc being made using the followingsequence of steps. The first step includes forming for each compositedisc at least three support layers, each support layer having a supportlayer surface formed with information indicia. Next, an informationlayer on each of said support layer surfaces. The information layer fromone of the support layers is transferred to the information layer ofanother support layer. Finally, the other support layer (which now hasnow two information layers) is attached to the third support layer, in aback-to-back relation. A spacer layer is added between the twoinformation layers that are mounted on the same substrate. In addition aprotective layer is added on the bottom of some of the informationlayers. The two support layers of the final disc can then be joined bybonding the surfaces with the protective layers.

[0012] The manufacturing line for manufacturing a plurality of compositediscs continuously includes a first injection press adapted to form aplurality of first and second support layers; and a second injectionpress adapted to form a plurality of third support layers, each of thelayers having a top surface with information indicia and a bottomsurface. The manufacturing line further includes an information layerstation receiving the support layers and forming information layers onthe support layers. A joining station is arranged to receive and jointhe first and third support layers temporarily, with the respectiveinformation layers being positioned in a facing relationship. Aseparating station is adapted to receive the joined support layers andto separate the third layer while leaving the respective informationlayer of the third layer attached to the first support layer. Finally abonding station is adapted to receive the first support layers with twoinformation layers and said second support layers and to bond is theminto composite disks. Preferably transport means, including conveyorbelts, are used to transport the support layers between the stations ofthe manufacturing line. The line also includes a protective layerstation adapted to add a protective layer to the support layers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1a shows a somewhat diagrammatic cross-sectional view of acomposite DVD/CD disc constructed in accordance with this invention,with the DVD substrate being a multi-layered substrate;

[0014]FIG. 1b shows a somewhat diagrammatic cross-sectional view of acomposite DVD/DVD disc constructed in accordance with this invention,with at least one of the DVD substrates being a multi-layered substrate;

[0015]FIG. 2 shows a block diagram of an assembly line used to makecomposiute DVD/CD discs of the type shown in FIG. 1a;

[0016]FIGS. 3a-3 g show cross sectional views of various intermediatediscs during the manufacturing process; and

[0017]FIG. 4 shows a flow chart describing the process used to generatecontinuously a plurality of composite discs, each disc being similar tothe one shown in FIG. 1a.

DETAILED DESCRIPTION OF THE INVENTION

[0018]FIG. 1a shows a DVD/CD composite disc 10. Disc 10 has a diameterof about 12 cm and is formed of two substrates 12 and 14 joined by abonding layer 16. In the embodiment of FIG. 1a, substrate 12 is the CDsubstrate, substrate 14 is the DVD substrate. The CD substrate 12 isabout 1000 microns thick and the bonding glue is about 50 microns thick.The thickness of the DVD component depends on its number of informationlayers. A DVD-5 substrate has only a single information layer and isabout 600 microns thick resulting in a disc having an overall thicknessof about 1,650 microns (obviously FIG. 1a is not to scale). Thisthickness is compatible with most DVD and CD players, and, accordingly,a disc with a DVD-5 substrate can be played by most of these players.However, a standard DVD-9 substrate has a thickness of about 1200microns. If such a substrate were used for a composite disc, the overallthickness of the disc would be 2250 microns, which would not be useablein most CD or DVD players. Accordingly, in the present invention, theDVD substrate 14 is a dual layer DVD-9 substrate having a specialstructure as disclosed in U.S. Pat. No. 6,117,284 (the '284 patent),incorporated herein by reference. The resulting composite disc is only1680 microns, still well within the limits of most players.

[0019] Therefore preferably, the DVD substrate 14 is a high datacapacity, i.e., it's a DVD-9 or higher, but has the special structuredisclosed in the '384 patent.

[0020] As shown in FIG. 1a, CD substrate 12 is formed of a transparentsupport layer 20, an information layer 22 and a protective layer 24. Theinformation layer 22 is formed with various surface pits and land areasin accordance with the standard CD specifications, and referred toherein as information indicia. These indicia have been omitted for thesake of clarity.

[0021] The DVD substrate 14 is formed of the following layers:

[0022] a transparent support layer 26;

[0023] a first information layer 28;

[0024] a spacer layer 30;

[0025] a second information layer 32; and

[0026] a protective layer 34.

[0027] Information layers 28 and 32 also information indicia formed inaccordance with standard DVD specifications, which again have beenomitted for the sake clarity. Information layer 28 is semi-transparent,to allow a laser beam (not shown) to read the second information layer32.

[0028] The two transparent support layers 20, 26 allow a laser beam tobe directed to the respective information layers in a manner well knownin the art.

[0029] The spacer layer 30 is also an adhesive layer used to secure theinformation layer 32 during manufacturing, as discussed in more detailbelow.

[0030]FIG. 2 shows schematically the elements of a disc manufacturingline 100 used to make a dual layer disc in accordance with thisinvention. The manufacturing line consists of several stations, eachstation being provided with apparatus designed to perform a specificfunction. Discs are transported from one station to another by conveyorbelts or other similar means known in the art. In the followingdescription, the means for transporting discs are referred to asconveyor belts for convenience, it being understood that thetransporting means may involve other mechanisms as well, includingrotating wheels with slots for receiving discs, etc.

[0031] As indicated in FIG. 4, the first step 200 in the process is themaking of support three layers: support layer 20 for the CD substrate12, support layer 26 for the DVD substrate 14 and intermediate supportlayer 40 which is not incorporated in the final dual layer disc. Thesesupport layers are depicted in FIGS. 3a, 3 b and 3 c, respectively. Eachof these support layers has a respective top surface that hasinformation pit and land areas as described above. The support layers 20and 26 are made of a transparent plastic material, such as polycarbonate(PC) while intermediate support layer 40 is made of polymethylmethacrylate (PMMA) or other similar material which does not bond wellwith materials used for the information layers, such as aluminum. Thesupport layers 20, 26 are made in an injection press 102, which makesuse of multi-cavity type device using two molds using techniques wellknown in the art. Intermediate support layer 40 is made by a separateinjection press 104. Details of how these layers are made can be foundin above-mentioned U.S. Pat. No. 6,117,284.

[0032] The support layers from injection press 102 are deposited on aconveyor belt 106 while the support layers 40 are deposited on aconveyor belt 108. Next, in step 204 the information layers 22, 28 and32 are deposited on support layers 20, 26, 40, respectively, as shown inFIGS. 3a-3 c, resulting in intermediate discs I1, I2 and I3, as shown.In FIG. 2, step 204 is accomplished by passing the support layers 20, 26under a metalizer 110 by conveyor belt 106. Similarly, support layer 40is passed under a metalizer 112 by conveyor belt 108. The metalizers110, 112 deposit a reflective metallic layer, made for instance ofaluminum, using sputtering or other similar techniques.

[0033] The metallized layers are shown in FIGS. 3a-3 b and aredesignated as intermediate discs I1, I2 and I3.

[0034] Next, the intermediate discs are fed to a sequencer 114. Thepurpose of the sequencer 114 is to align the intermediate discs in aparticular sequence (step 206) on two separate conveyor belts 116, 118.Conveyor belt 116 is used to carry intermediate discs I2 and conveyorbelt 118 carries intermediate discs I1 and I3.

[0035] Discs I1 and I3 are fed to a bonding station 120 where the twodiscs are joined (step 208). For this purpose, the spacer layer 30 isapplied to the layer 28 of each disc I1 resulting in an intermediatedisc I4. Before the material of this layer is set, or hardens, theintermediate disc I3 is applied to or pressed against I1 with the spacerlayer 30 being in intimate contact with layer 32, as shown in FIG. 3d.The resulting intermediate disc I5 has five layers as shown in FIG. 3e.Discs I5 are carried to the next station, which is a surface transfermodule, by a conveyor belt 122.

[0036] Surface transfer module 124 is used to finalize the transfer ofinformation layer 32 so that it remains joined to the spacer layer 30(step 210). This process is facilitated by the material of support layer40 which does not stick to the metallic layer 32. Between steps 204 and210, information layer 32 is maintained on support layer 40 by adhesioncaused by molecular roughness at the interface between these layers. Instep 210, the intermediate support layer 40 is separated and pulled awayfrom information layer 32, as shown in FIG. 3e. The support layer cannow be discarded, or reused to make and carry another information layer.The result is a four-layer intermediate disc 16 which is deposited onconveyor belt 116.

[0037] Next, in step 212 protective layers 24 and 34 are added tointermediate discs I2,I6 using protective layer station 126. Theresulting intermediate discs I7,I8, shown in FIGS. 3f and 3 grespectively.

[0038] In step 214 the discs I7,I8 are provided to a rebonding station128. At this station, the two intermediate discs I7 and I8 are joined bybonding layer 16. The end result of step 214 is dual layer disc 10. Fromstation 128 the discs 10 are transferred to other stations(not shown)for labeling (step 216) and/or other finishing processes. Thus, themanufacturing line 100 is capable of producing dual layer discs havingthe structure indicated in FIG. 1a in a continuous manner. Obviouslyother types of discs may be made as well, using a manufacturing linehaving the appropriate stations, as required. For example, FIG. 1b showsa cross-sectional view similar to FIG. 1b with a composite DVD/DVD disc.In this case, the discs made of PC are made by one injection presssimilar to press 102, PMMA discs are made by a second injection presssimilar topress 104, all the discs are coated with a reflectivematerial, and then joined as described above.

[0039] Obviously numerous modifications can be made to this inventionwithout departing from its scope as defined in the appended claims.

1. A method of manufacturing a composite disc including at least twosubstrates accessible by a laser beam from opposite sides of the disc,including a first substrate with at least two information layers and asecond substrate with at least one information layer, said methodcomprising: forming for each disc at least three support layers, eachsupport layer having a support layer surface formed with irregularitiesdefining information; forming an information layer on each of saidsupport layer surface; transferring said information layer from onesupport layer to the information layer of another support layer; joiningsaid another support layer with the third support layer, in aback-to-back relation.
 2. The method of claim 1 further comprisingjoining said information layers with a spacer layer.
 3. The method ofclaim 1 further comprising adding a protective layer to said anothersupport layer and said third layer.
 4. The method of claim 1 furthercomprising joining said another support layer and said third layer withan adhesive layer.
 5. A method of making composite discs continuouslycomprising: forming a first, a second and a third support layersubstantially concurrently; adding an information substrate to eachsupport layer; joining said first and second support layer with therespective information layer being disposed in an adjacent relationship;removing said second support layer from its information layer; andjoining said first and third layer in a back-to-back relation to makesaid first and second information layers accesible for reading by alaser beam from one side, and said third information layer from theother side.
 6. The method of claim 5 further comprising adding a spacerlayer between the information layers of said first and second substrate.7. The method of claim 5 wherein said support layers each have a top anda bottom surface, with said information layers added to said topsurfaces, further comprising adding a protective layer on said bottomsurfaces.
 8. The method of claim 7 further comprising adding a bondinglayer arranged to join said protective layers.
 9. A method of makingcomposite discs continuously, the method comprising: forming a first anda second support layer, each said first and second support layers beingdisc shaped and having a first surface with information indicia and asecond surface; forming a third support layer, said third support layerhaving a first surface with information indicia and a second surface,said third support layer being made of a different material then saidfirst and second support layers; adding a respective first, second andthird information layer to said first, second and third support layers;positioning said first and third support layers in a facingrelationship, with said first and third information layers beingadjacent; separating said third support layer from said thirdinformation layer; and joining said first and second support layers. 10.The method of claim 9 wherein said method is performed on amanufacturing line including a plurality of stations, wherein eachstation is devoted to performing one of said steps of said method. 11.The method of claim 9 further comprising providing protective layers onsaid bottom surfaces.
 12. The method of claim 9 wherein said first andsecond support surfaces are made of a first material and said thirdsupport surface is made of a second material different from said firstmaterial.
 13. The method of claim 12 wherein said second material is notadhesive to said information layers.
 14. A manufacturing line formanufacturing a plurality of composite discs continuously comprising: afirst injection press adapted to form a plurality of first and secondsupport layers; a second injection press adapted to form a plurality ofthird support layers, each said layers having a top surface withinformation indicia and a bottom surface; an information layer stationreceiving said support layers and forming on said support layersinformation layers; a joining station arranged to receive said supportlayers with said information layers to join said first and third supportlayers temporarily, with the respective information layers beingpositioned in a facing relationship; a separating station adapted toreceive the joined support layers and adapted to separate said thirdlayer while leaving the respective information layer of the third layerattached to the first support layer; and a bonding station adapted toreceive said first support layers with two information layers and saidsecond support layers and to bond them into composite discs.
 15. Themanufacturing line of claim 14 further comprising transport meansadapted to transport said support discs between said stations.
 16. Themanufacturing line of claim 14 further comprising a protective layerstation adapted to add a protective layer to said support layers.